The genesis of any map is rooted in the specific agenda that it is meant to achieve. It is argued that clarifying one’s objectives is fundamental to the practice of developing maps as it defines the subsequent processes of data identification and content representation (Harley, 1989; Krygier and Wood, 2016).
Map 1 was conceived from the objective of highlighting areas where concentrations of the urban poor are disadvantaged by low levels of access to public transportation in London. Map 1 therefore made use of TfL’s Public Transport Accessibility Level (PTAL) scores and data on income deprivation collated by government sources, as they were relevant indicators reflecting the real-world phenomena of interest and the data had been aggregated according to widely-used statistical boundaries. To maximise its utility, both datasets should ideally be overlaid with one another, and hence a bi-variate choropleth map was chosen as the medium of representation.